America is the land of plenty—plenty of food, plenty of overweight men and women, and plenty of weight loss plans. The need for effective weight loss programs is great, as 66.5% of American adults are overweight or obese, and being overweight is linked to high blood pressure, diabetes , heart disease, and osteoarthritis , among other health concerns. However, there is little scientific evidence as to how the various weight loss plans compare to one another.

A group of British researchers compared four popular weight loss plans. After six months, the four plans were equally effective at promoting weight loss. But by twelve months, those that incorporated support—weekly meetings or exercise classes—were most successful. These findings appear in the June 3, 2006 issue of the British Medical Journal .

About the Study

British researchers enrolled 300 overweight people in a study to compare popular weight loss programs. The volunteers were randomly assigned to one of four diet plans or the control group:

  1. Slim-Fast–shakes or bars eaten in place of one or two meals per day
  2. Dr. Atkins’ New Diet Revolution –low carbohydrate eating plan detailed in this book
  3. Weight Watchers Pure Points Program–calorie-controlled eating combined with weekly group meetings
  4. Rosemary Conley’s Eat Yourself Slim Diet and Fitness Plan–low-fat diet combined with weekly exercise classes
  5. Control Group–maintain current diet and exercise pattern

Researchers compared weight changes among the groups at six and 12 months.

At six months, the four weight loss plans were equally effective with an average loss of 13.2 pounds. Each diet group lost significantly more weight than the control group.

Among the volunteers who returned for the 12-month follow-up, researchers saw a distinct division—people in the “supported” programs (Weight Watchers and Conley’s plan) showed greater success than those assigned to the do-it-yourself plans (Dr. Atkins and Slim-Fast). The success was two-fold. People in the supported groups were more likely to stick to their programs for at least one year (35% vs. 15% of the do-it-yourself-ers), and were less likely to regain weight. On an individual level, people who stuck with any diet plan for one year lost about 10% of their body weight.

This study was the basis for a reality TV show, BBC Diet Trials . The BBC covered the cost of participation for the first six months only, which may have affected compliance rates during the last six months (54% of volunteers returned for the 12-month follow-up).

How Does This Affect You?

Does this mean that Weight Watchers is the only way to go? No. Weight Watchers is a good option, but is not the only option for weight loss. While people in this study were more likely to stick with a program like Weight Watchers that includes group support and/or exercise classes, the people who fared the best were those who stuck with any program for at least one year.

The key is to find a program you can commit to long-term, one that fits with your lifestyle, personality, and health status. When choosing a program, know that the safest and most effective weight-management plans combine physical activity with balanced, portion-controlled eating (talk with your doctor before trying such restrictive plans such as Dr. Atkins or Slim-Fast).

This study also found that those who stuck with their diets for 6-12 months lost a “clinically useful” amount of weight. This amount—5-10% of body weight—is associated with reductions in blood pressure and waist circumference, and can therefore help lower the risk of cardiovascular disease.